1. Field
The described technology relates generally to an organic light emitting diode display. More particularly, the described technology relates to an organic light emitting diode display that makes use of a refractive index.
2. Description of the Related Technology
Organic light emitting diode displays have self-emissive characteristics, and have a relatively small thickness and weight due to not requiring a separate light source. Organic light emitting diode displays generally exhibit high-quality characteristics such as low power consumption, high luminance, high response speed, etc.
Conventional organic light emitting diode displays generally include a first substrate having an organic light emitting diode and a second substrate facing the first substrate and protecting the organic light emitting diode of the first substrate. The organic light emitting diode includes an organic emission layer for emitting light, and a first electrode and a second electrode, which face each other, with the organic emission layer interposed therebetween.
Conventional organic light emitting diode displays are classified into (1) a top emission type, in which light emitted from the organic light emitting diode is irradiated in the direction of the second substrate, (2) a bottom emission type, in which light emitted from the organic light emitting diode is irradiated in the direction of the first substrate, and (3) a double-side emission type, in which light emitted from the organic light emitting diode is irradiated in the directions of both the first and second substrates.
In a top emission type of display, the organic light emitting diode generally has a structure in which the first electrode is light reflective and the second electrode is semi-transmissive. Such a top emission type organic light emitting diode display has a microcavity structure.
When an organic light emitting diode display becomes larger in size, it is generally difficult to realize a large-sized organic light emitting diode display of a top emission type. The difficulty is related to the fact that the second electrode is generally made of a thin film in order to make it semi-transmissive, and the it usually needs to be formed as one layer over the entire organic light emitting diode display. In large organic light emitting diodes, sheet resistance of the second electrode increases, making the flow of current through the second electrode less smooth.
Due to the difficulty above, larger size organic light emitting diode displays are generally of a bottom-emission type, which can make the thickness of the second electrode sufficiently large.
Bottom emission type organic light emitting diode displays generally have lower luminous efficiency and color reproduction when compared to top emission type organic light emitting diode displays.
In recent years, a bottom emission type organic light emitting diode display with different thicknesses for each organic emission layer, according to the wavelength of light (red, green, or blue light) emitted from each organic emission layer has been developed. In such displays, a deposition process using an additional mask is generally used in order to vary the thickness of each organic emission layer, thereby increasing the overall manufacturing time and complexity.
The above information disclosed in this Background section is only for enhancement of understanding of the background of the described technology and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.